Math Problem Statement

Solve step by step doing by yourself all necessary calculations xy’’’-xy’+2y=0

Solution

To solve the differential equation xyxy+2y=0xy''' - xy' + 2y = 0, we'll use a method that is often applied to such equations, assuming a solution of the form y=xry = x^r. This is because the given equation is homogeneous and its coefficients are functions of xx.

  1. Assume a solution of the form y=xry = x^r: y=xry = x^r Then, y=rxr1y' = r x^{r-1} y=r(r1)xr2y'' = r(r-1) x^{r-2} y=r(r1)(r2)xr3y''' = r(r-1)(r-2) x^{r-3}

  2. Substitute these into the differential equation xyxy+2y=0xy''' - xy' + 2y = 0: x(r(r1)(r2)xr3)x(rxr1)+2(xr)=0x \left( r(r-1)(r-2) x^{r-3} \right) - x \left( r x^{r-1} \right) + 2 \left( x^r \right) = 0

  3. Simplify each term: xr(r1)(r2)xr3=r(r1)(r2)xr2x \cdot r(r-1)(r-2) x^{r-3} = r(r-1)(r-2) x^{r-2} xrxr1=rxrx \cdot r x^{r-1} = r x^r 2xr=2xr2 x^r = 2 x^r

  4. Substitute back into the equation: r(r1)(r2)xr2rxr+2xr=0r(r-1)(r-2) x^{r-2} - r x^r + 2 x^r = 0

  5. Combine like terms: r(r1)(r2)xr2rxr+2xr=0r(r-1)(r-2) x^{r-2} - r x^r + 2 x^r = 0 Notice that the powers of xx must be the same for all terms to combine. Rewrite rxrr x^r and 2xr2 x^r in terms of xr2x^{r-2}: r(r1)(r2)xr2rxr+2xr=0r(r-1)(r-2) x^{r-2} - r x^r + 2 x^r = 0 r(r1)(r2)xr2rxr+2xr=0r(r-1)(r-2) x^{r-2} - r x^r + 2 x^r = 0

    Since xr2x^{r-2} and xrx^r are different powers of xx, equate coefficients to zero separately. Therefore, we only need to equate the polynomial coefficients to zero:

  6. Form and solve the characteristic equation: r(r1)(r2)=0r(r-1)(r-2) = 0

    The roots are: r=0,r=1,r=2r = 0, \quad r = 1, \quad r = 2

  7. Construct the general solution: Since we have three distinct roots, the general solution to the differential equation is: y(x)=C1x0+C2x1+C3x2y(x) = C_1 x^0 + C_2 x^1 + C_3 x^2 y(x)=C1+C2x+C3x2y(x) = C_1 + C_2 x + C_3 x^2 where C1C_1, C2C_2, and C3C_3 are arbitrary constants.

Thus, the general solution to the differential equation xyxy+2y=0xy''' - xy' + 2y = 0 is: y(x)=C1+C2x+C3x2y(x) = C_1 + C_2 x + C_3 x^2

Would you like more details or have any questions? Here are some related questions you might consider:

  1. What is the method used to solve this differential equation called?
  2. How would you solve a similar differential equation with different coefficients?
  3. Can you provide an example of a non-homogeneous differential equation?
  4. How does the solution change if one of the roots of the characteristic equation is repeated?
  5. What if all roots of the characteristic equation are the same?
  6. Can you verify the solution by substituting it back into the original differential equation?
  7. What are some applications of differential equations in real-world problems?
  8. How would the approach change if the differential equation had variable coefficients?

Tip: When solving differential equations, always verify your solution by substituting it back into the original equation to check for consistency.

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Math Problem Analysis

Mathematical Concepts

Differential Equations
Homogeneous Equations
Characteristic Equation

Formulas

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Theorems

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Suitable Grade Level

Advanced Undergraduate